1. Field of the Invention
The present invention relates to a numerical controller, and particularly to a numerical controller having the function of managing the life of a tool based on machining conditions.
2. Description of the Related Art
Generally, in a tool used in a machine tool, the cutting edge thereof wears and cutting resistance increases with increasing machining time. Advanced wear decreases machining accuracy, and a predetermined machining accuracy required for a workpiece cannot be maintained. Thus, the tool reaches the end of the life thereof.
As prior art techniques relating to tool life, Japanese Patent Application Laid-Open No. 2003-308106 and International Publication No. WO2000/012260 disclose techniques in which a tool life to be consumed when a machining program is executed is estimated based on machining conditions and the like before machining. Using the above-described prior art technique, an operator who performs machining can avoid the problem that the life of a tool unexpectedly ends during machining by preparing a tool having a life longer than a tool life consumed during machining in a tool magazine in advance.
Tool-life consumption-speed changes in accordance with machining conditions such as coolant concentration, pH, temperature, and machine's internal temperature. Accordingly, in the case where machining conditions assumed when tool life is estimated (that is, before machining start) are different from machining conditions at the time of an actual operation or in the case where machining conditions change during an operation, the tool life is consumed faster than estimated, and the tool life may end during machining. This problem cannot be solved even if the aforementioned techniques disclosed in Japanese Patent Application Laid-Open No. 2003-308106 and International Publication No. WO2000/012260 are used.